Compressed Load Question..

[jerkface11]

Work up the load separately for the different brass.

 

[JimKirk]

smaller volume LC brass.

it is not ...

.223/5.56 Case Capacity ... I cant get this chart to line up here ... but the right most three numbers are H2O Capacity ....

Case Manufacturer Case Weight* H20 Capacity**
Lake City 06 92.0 30.6
WCC99 95.5 30.5
Sellier & Belloit 92.3 30.5
Remington 92.3 30.4
PMC 93.5 30.4
Hirtenberger 93.7 30.4
Lake City 04 93.0 30.4
Federal 96.3 30.2
Hornady 93.9 30.1
IMG (Guatemalan) 95.4 30.1
Lapua (new lot) 93.4 30.1
Winchester 93.9 30.1
Olympic 97.4 30.0
Radway Arsenal 96.1 30.0
PMP 104.5 29.9
FNM 93-1 97.3 29.8
Lapua (old lot) 104.0 28.0

 

[MCMXI]

JimKirk, are those capacities for fired cases or full length resized cases?

 

[JimKirk]

Full length sized and trimmed to 1.750" ... a fired primer was inserted .... weighed ... and cases filled with distilled water then weighed again ... the H2O capacity would be the filled weight minus the first weight...

This info all come from this link .... http://www.6mmbr.com/223rem.html you will have to read on down about 1/3 the way down to see the charts...

Lots of folks get the .223(Less)/5.56(more) case capacity crossed with the .308Win(more)/76.2x51(less) case capacity which is opposite....

 

[Andrew Leigh]

For the case volume to make sense, or to be of use, it should be fire formed as this is the accurate measure of the case when under operation and reflects the chamber dimensions.

 

[RN]

Guys,

Again, understanding that I am somewhat new to this I have a question about fireformed brass..I understand what it iss and that it contributes to brass longevity but what's the process..

If I go to the range today and shoot 300 rounds of FL sized brass, would I then come back to the bench and just neck size those, reload, and shoot again?

 

[jwrowland77]

Guys,



Again, understanding that I am somewhat new to this I have a question about fireformed brass..I understand what it iss and that it contributes to brass longevity but what's the process..



If I go to the range today and shoot 300 rounds of FL sized brass, would I then come back to the bench and just neck size those, reload, and shoot again?

Yep. It's that easy. I still go through all my brass prep steps like trimming etc etc. but yep, just clean, neck size and trim. I use a Lee Collet neck die that helps keep the neck in better alignment.

I've noticed a 40fps difference between my neck sized fire formed brass and my FL resized with FL resized being faster.

I said all that to say this, you may have to adjust your load a bit with fire formed brass as compared to FL resized brass.

 

[RN]

Hummm...

Since I only shoot .223 out of my DDMV5 I guess that would be a lot easier in the brass..I like it...Thx!!

Now, do I need a dedicated neck sizing die or is there some trick with using one I already have? Also, what adjustments in load? Up? Down?

If I bought an X die(do they make a neck sizer?) I could just clean, size, and load...

 

[jwrowland77]

Let me clarify too. If you're using the brass in a semi-auto, FL resize every time.

Neck sizing, save for single shot and bolt actions.

And yes, get a dedicated neck sizing die.

 

[Reloadron]

I can see where loading 22.5 to 23.5 grains of Varget Powder would come close to filling a 223 Remington case. It really depends on the powder drop. I see things going a little like this:

The VMD (Volume Metric Density) of Varget powder is right around .07310. Each powder has a VMD. If we multiply the VMD times the powder weight in grains we will get the powder volume in CC (Cubic Centimeters). So we get in this case:

.07310 (VMD Factor) * 22.5 (grains of powder) = 1.64475 Cubic Centimeters of powder
.07310 (VMD Factor) * 23.5 (grains of powder) = 1.71785 Cubic Centimeters of powder

Looking at the chart JimKirk was kind enough to provide the chart list 17 different cases and the volume of each case expressed in grains of water. If we add up all 17 cases we get about 511.5 grains and divide that by the 17 cases we get:

511.5 / 17 = 30.088 for the average grains of water. So we can say the average 223 Remington case holds 30.088 grains of water. To convert grains to grams we multiply grains by .06479891 so:

30.088 * .06479891 = 1.9496693 grams

1.0 gram of water = 1 CC of water so the average case capacity of 223 Remington is 1.9496693 Cubic Centimeters.

Granted all of these numbers I have gotten carried away with expressing numbers to the right of the decimal point. Anyway all of these numbers are close but when calculating the VMD of powder the numbers would be for a chunk of powder which is not how powder really comes. VARGET features small extruded grains. When the powder is dropped in the case those small extruded grains have air between them so if we say for example 22.5 of Varget = 1.64475 CC or that 23.5 grains of Varget = 1.71785 CC that assumes a chunk of Varget. While not perfect it's close enough.

When we fill a case with water to measure case volume the water is filled all the way to the case mouth at the very top of the case neck. A portion of that volume will be used by the seated bullet. We won't even get into that but if the bullet has a flat base we could measure the bullet OAL and do some math and see how much case volume the bullet when seated displaces.

Something else that comes to mind is the actual powder drop. Powder dropped from a higher height will settle more in the case on the initial drop. Also if we drop powder and then gently shake the case the powder will settle. The same amount of powder will use less case volume. It is not unusual for hand loaders who load precision powder drops that will be compressed loads to use extender tubes on their powder drops. They look like the below image:



The fact that reloading manuals do not call out 22.5 or 23.5 grains of Varget as a "C" Compressed load doesn't mean anything. It simply means looking at a typical 223 case having a volume of about 1.95CC will hold 23.5 grains of Varget without compressing the charge when a specific bullet is seated. As a side note my Hornady 9th Edition does show 23.5 grains of Varget as a Max charge when using Hornady 75 grain A Max and BTHP bullets loaded to a COL of 2.390" and 2.250" respectively.

In conclusion 23.5 grains of Varget will have a volume of about 1.72CC while a 223 case has a volume of about 1.95CC including the neck. That only leaves .23CC of volume left.

Yeah, boring but that is how it works out.

To answer the Original Poster's Question:

Hi Guys,

Ok..I was loading up some .223 tonight with 75gr HPBT's with Varget. My cases are a mix of CBC,(5.56) LC 13,(5.56) and RP(.223).. Started at 22.5 and worked up to 23.5..

I noticed that the case on the military rounds are more filled than the .223 and I am sure this is due to the brass being thicker in the 5.56 cases. On those, its basically a compressed charge even though it's well below "max" according to Hodgen and Lee..

Anyone give me some info on this type of situation? Safe? Not safe?

I wouldn't worry about it. The effect you are seeing is normal. I would keep in mind that the 23.5 grain load looks to be a maximum load in my Hornady 9th edition so I would approach that load with caution. I would just follow the load data for the bullet you are loading. Will reduced case volume increase pressure for a given load? Yes, absolutely it will. How much will it increase pressure? I doubt enough to worry about but that just brings us back to observing good and safe loading practices.

Ron

 

[JimKirk]

For the case volume to make sense, or to be of use, it should be fire formed as this is the accurate measure of the case when under operation and reflects the chamber dimensions.

But RN should be working with full length sized cases in an AR type rifle ... not fire formed cases ... he will have to deal with the volume of that sized brass as far as compressing/not compressing powder when reloading... while it is true that the shape of the chamber would have an effect upon firing...

I do want to add that I have no LC brass that is newer than 2011 ... so there may be some heavy LC brass out there ...

 

[MCMXI]

RN, my favorite .223 Rem load is 24.0gr of Varget with a 77gr SMK bullet (loaded to magazine length) in a variety of .223 Rem cases including Remington, Winchester and Federal. This is a compressed load but it's a known good performer in numerous AR rifles.

Reloadron, I have to wonder about the 5 decimal places in the VMD chart in the link below.

http://www.leeprecision.com/cgi-data/instruct/VMD'S.pdf

 

[Berger.Fan222]

Work up the load separately for the different brass.

Agreed. You need to work up a new load for different types of brass. Using Min loads is probably ok for plinking loads with mixed brass, but if you want to approach max loads, you need to work up loads independently for every different set of components. You'll never have much precision mixing brass.

 

[Andrew Leigh]

But RN should be working with full length sized cases in an AR type rifle ... not fire formed cases ... he will have to deal with the volume of that sized brass as far as compressing/not compressing powder when reloading... while it is true that the shape of the chamber would have an effect upon firing...

I do want to add that I have no LC brass that is newer than 2011 ... so there may be some heavy LC brass out there ...

Correct

 

[Reloadron]

RN, my favorite .223 Rem load is 24.0gr of Varget with a 77gr SMK bullet (loaded to magazine length) in a variety of .223 Rem cases including Remington, Winchester and Federal. This is a compressed load but it's a known good performer in numerous AR rifles.

Reloadron, I have to wonder about the 5 decimal places in the VMD chart in the link below.

http://www.leeprecision.com/cgi-data/instruct/VMD'S.pdf

I agree as to 5 places to the right of the decimal as to the VMD and thus used them. The point of my post was take for example full length sized 223 brass verse for example a once fired case that has been fire formed to the size of a chamber. How much will the case volume actually change? Take a look at the data JimKirk posted. There were 17 different cases and that discounts that case volume changes lot to lot and even within a lot by a single manufacturer. That is a given. So using JimKirk's data chart I added up all 17 examples and got an average.

Does anyone have a loading manual that calls out a single specific case for their load data? I have never seen one. So when load data for say a 223 Remington case is compiled I wonder what those compiling the data use for a case volume number? My guess (and only a guess) would be 30CC simply because that is about the average.

The question isn't if case volume changes from case to case, we know it does, but does that change have enough significance to worry about? My guess is no it doesn't matter and any change will not come in light of loading the cartridge case.

All of that just gets us back to square number one as to developing and practicing good hand loading practices.

Case #1 in the chart held 30.6 grains of water and case #17 held 28.0 grains of water. So the difference between case #1 and Case #17 was 2.6 grains of water. That is about 0.168CC of volume in the cases between the Max and Min case volume. That is a given so when loading identical powder charges in both cases how much difference will that make in chamber pressure? More important is will that difference even matter? Will it be significant in light of the cartridges intended use? Will my rifle explode?

Now I seat a bullet in those cartridges. How about the case neck thickness of that brass? I have a piece of LC NATO 5.56 brass here dated 89. Case neck thickness is .011", I also have a Remington 223 case and neck thickness is .012" and finally a WCC 5.56 NATO case dated 13 with a neck thickness of .011". So if I run all three cases through the same die I figure the Remington commercial brass will have a greater neck tension than the remaining two. How much will it matter? Shouldn't it take more pressure to break neck tension on the Remington case than the remaining two? Just another variable.

Now with that said the lowly little primer will be charged with the responsibility of igniting my powder charge. Primer brisance comes into play, as if we didn't have enough variables. Primer brisance like brass varies from lot to lot within a manufacturer and primer to primer within any given lot. Note the differences in small rifle primer brisance which can be seen here. My guess is that will also contribute to a change in the pressure curve of the powder burn.

The point with all of this and yes, there is a point is that if we follow good hand loading practices none of the variables will matter enough to matter. If good practices are used none of these variables will cause the gun to explode like a hand grenade.

Ron

 

[Andrew Leigh]

Case #1 in the chart held 30.6 grains of water and case #17 held 28.0 grains of water. So the difference between case #1 and Case #17 was 2.6 grains of water. That is about 0.168CC of volume in the cases between the Max and Min case volume. That is a given so when loading identical powder charges in both cases how much difference will that make in chamber pressure? More important is will that difference even matter? Will it be significant in light of the cartridges intended use? Will my rifle explode?

75gr Hornady, 22gr. Varget and 30.6gr H2O case capacity.
Pressure 40 158psi and a speed of 2 639fps

75gr Hornady, 22gr. Varget and 28.0gr H2O case capacity.
Pressure 49 362psi and a speed of 2 750fps

An increase in pressure of 9 204psi (22.9%) which adds 111fps so yeah, I would say it makes a difference. Rather than looking at the amount of volume increase look at the % change 30.6/28=9.2% of case volume.

Now imagine if you had a hot load and popped in a small capacity case. Case volume variations mean more on smaller cases.

On primers I did a test on my .375 with hot loads. The difference between a LRM and LR primer was a maximum of 35fps, this could be more significant on a smaller case?

 

[Reloadron]

Andrew, how did you derive the chamber pressures? The actual accurate measuring of pressure is something I have interest in and am curious about.

Thanks
Ron

 

[Andrew Leigh]

Hi Ron,

I simply entered the generic information into QuickLOAD which then calculates the pressure based on the powder, charge weight, seating depth, bullet type and weight and the internal case volume. If one chrony's the load then you can feed the data in, calibrate the powder burn rate and then get a calculated number very, very close to actual.

I used the standard SAAMI spec's, for more accurate data then one must complete the real data. Here is a screenshot of a typical load in Quickload.

 

[Reloadron]

Andrew, this is something that has always piqued my curiosity. Quick Load does somehow derive a chamber pressure and as the saying goes how do it do that? Most ballistic formulas can be found online or in Hatcher's notes. I have looked at information like what is found here I can appreciate that any formula can't give a perfect number and am good with that I just question how close to true numbers this stuff is? I mean if this can all be solved by crunching numbers why bother to strain gauge or pizeo gauge a barrel? I mean some numbers are a given and easy to calculate, like FRE (Free Recoil Energy) or Muzzle Energy. I am just curious as to what formula(s) QuickLoad is using to derive chamber pressure from what the user inputs?

Anyway thanks for the enlightening information and I don't want to drag this thread off topic with my questions.

Ron

 

[Andrew Leigh]

Ron, you have mail.

 

[Reloadron]

Ron, you have mail.

Not seeing any mail yet.

I did just start a thread on QuickLoad. Thinking real hard about buying it. It seems to be well supported. I know we have several members using it who seem to like it.

Ron

 

[jwrowland77]

I'm going to have to break down and order me Quickload. I'm really interested in seeing what my match ammo load is at that I use for my 1000yd load.

 

[Reloadron]

Andrew, many thanks for a very informative email. I did reply.

This is the time of the year in NE Ohio, USA where I live I dislike. We get ready for winter and snow moving my beloved outdoor rifle shooting off the snow covered range. So many things I wanted to test and never got to.

I did start a thread on QuickLoad but at this point, after a year of debate, figure I may as well just buy it. Many thanks again Andrew for the information.

Ron